Is it bigger than a breadbox? Probing stellar secrets by modelling spectra of magnetic and other stars

天空中最明显的天体，我们的太阳，是一颗典型的恒星。在晚上，我们在天空中看到的大部分是其他的恒星，它们和我们的太阳很像，只是它们的大小、表面温度、距离等各不相同。在过去一个世纪的大部分时间里，许多天文学家一直在积极地试图获得有关单个恒星的信息（例如每颗恒星的质量），以了解恒星发光表面下的情况(内部有多热，密度有多大？物质是气态的吗？)，特别是要了解恒星是如何形成和变化的，并最终坍缩成巨大的热灰烬。了解恒星需要我们从它们发送给我们的微弱光线中尽可能多地提取信息。这种光包含了惊人的信息量。通过对光线的详细研究，我们通常可以发现恒星有多大，有多热，有多远，质量有多大。我们还可以得到关于表层（恒星的“大气层”）的更详细的信息，例如气体的密度，气体的化学成分，以及气体是安静的还是像刮风的日子一样冒泡和吹。我的总体研究计划集中在利用星光来尝试回答关于特定种类恒星的特定问题。例如，一些恒星被观察到被强磁场渗透。我正在观察一些恒星的磁场，这些恒星所处的环境使我们能够估计它们的年龄，并寻找这些恒星的平均磁性如何随着年龄的变化而变化的证据，从年轻的恒星到年老的恒星。回答这个问题将有助于我们理解恒星中的磁场是如何增长和变化的。我的计划的另一个方面是在白矮星中寻找非常弱的磁性。当像太阳这样的恒星耗尽燃料，坍缩成一个和地球一样大的“微小”天体，经过几个世纪的冷却，就会产生这些热恒星尸体。这将再次帮助我们更好地理解恒星的磁场。我也在观察那些非常年轻的恒星发出的光，它们周围仍然有一些气体，这些气体被引力聚集在一起形成了新的恒星。靠近恒星但尚未落到表面的气体被来自新恒星的光加热并发光。可以通过分析这种辉光来了解更多关于这种气体的信息——有多少物质，有多热，等等。我的研究的每一个方面都深入研究了一个关于恒星的非常小而具体的问题，但结果就像一个巨大的拼图游戏的碎片——把它们放在一起可以让我们更好地理解恒星如何形成和在它们的生命中变化的大故事

The most obvious astronomical object in the sky, our Sun, is a typical star. At night most of what we see in the sky is other stars, bodies much like our Sun except that they come in a wide variety of sizes, surface temperatures, distance, etc. For much of the past century, many astronomers have been actively trying to obtain information about individual stars (such as how much mass each has), to understand what stars are like below their glowing surfaces (How hot and how dense is the interior? Is the material gaseous?), and particularly to understand how stars form and change, and eventually collapse to huge hot cinders.***Learning about stars requires us to squeeze as much information as possible from the faint light they send to us. This light contains an astonishing amount of information. By studying the light in detail, we can often discover how large the star is, how hot, how far away, and how massive. We can also get more detailed information about the surface layer (the star's "atmosphere''), for example how dense the gas is, what the chemical composition of the gas is, and whether the gas is quiet or is bubbling and blowing like a windy day. ***My overall research programme focusses on using starlight to try to answer specific questions about specific kinds of stars. For example, some stars are observed to be permeated by strong magnetic fields. I am looking at the fields of a number of stars that are in environments which allow us to estimate their ages, and searching for evidence of how the average magnetism of these stars changes with age, from young stars to older ones. Answering this question should help us to understand how magnetic fields grow and change in stars. ***Another aspect of my programme involves looking for very weak magnetism in white dwarf stars. These are the hot stellar corpses that result when a star like the Sun runs out of fuel and collapses to become a "tiny'' body, about as large as the earth, that simply cools through the ages. Again this should help us to understand magnetic fields in stars better. ***I am also looking at the light from stars that are so young that they still have around them some of the gas that gravity pulled together to form the new star. The gas that is close to the star but has not yet fallen onto the surface is heated by the light from the new star, and glows. This glow can be analysed to find out more about that gas - how much material is there, how hot it is, and so on. ***Each of these aspects of my research digs into a very small, specific question about stars, but the results are like pieces of a huge jigsaw puzzle - putting them all together allows us to understand better the big story of how stars form and change through their lives.**